The Sant'Ignazio, which is open daily from 7:30 a.m. to 7 p.m. (though closed for lunch), is known for its ethereal ceiling. Recent visitors say to get the full effect of the exquisite ceiling, you should stand on the disk set into the floor of the nave. You'll find it just a few blocks west of the Trevi Fountain. Free guided tours are available on Tuesdays, Thursdays and Saturdays, from 3 to 6 p.m. For more information, visit the website.